Strange flickering Screen resolution issue

Hi
I have a hyundai w240d HD TFT, nvidia gforce 8800gt, recently i cannot get the resolution above 1024-800 if i do the screen flickers horizontally badly (only slightly on desktop), the problem becomes ten times worse when i view certain websites but not all or run some applications again not all, there are some white specs on the screen sometimes, which usually would indicate a graphics card problem, how ever the card has been tested on another system and is in full working order, i have changed the memory so no problem there either, i have formatted the drive reinstalled the operating system and change the cables from HD to TFT, i can watch video with no issues what so ever even when any web page is flickering behind the video I'm watching, when i rotate the screen view to vertical the problem remains horizontal.

Anny ideas welcome

No covered that

Do you have another monitor you could try hooking up to your system?

1 - No i don't have another hd screen to try it on which is a shame.
2 - Have already changed the cable no issue there.

I thaought mabe pcu or motherboard but every thing even the very latest games and programs run at full spec in low res without any glitches, but anything above 1024-768 and then the problem accurs.